U.S. patent application number 13/062195 was filed with the patent office on 2011-09-01 for end-of life circuitry.
This patent application is currently assigned to Switch Bulb Company, Inc.. Invention is credited to Carol Lenk, Ronald J. Lenk, Ethan Thorman.
Application Number | 20110210669 13/062195 |
Document ID | / |
Family ID | 42005386 |
Filed Date | 2011-09-01 |
United States Patent
Application |
20110210669 |
Kind Code |
A1 |
Lenk; Ronald J. ; et
al. |
September 1, 2011 |
END-OF LIFE CIRCUITRY
Abstract
An LED light bulb which turns itself permanently off when it
reaches the end of its useful life, and more particularly, to a
scheme which slightly varies the end-of-life condition from unit to
unit.
Inventors: |
Lenk; Ronald J.; (Woodstock,
GA) ; Lenk; Carol; (Woodstock, GA) ; Thorman;
Ethan; (Palo Alto, CA) |
Assignee: |
Switch Bulb Company, Inc.
San Jose
CA
|
Family ID: |
42005386 |
Appl. No.: |
13/062195 |
Filed: |
September 8, 2009 |
PCT Filed: |
September 8, 2009 |
PCT NO: |
PCT/US09/05021 |
371 Date: |
April 28, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61096253 |
Sep 11, 2008 |
|
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|
Current U.S.
Class: |
315/119 |
Current CPC
Class: |
H05B 45/58 20200101 |
Class at
Publication: |
315/119 |
International
Class: |
H05B 37/02 20060101
H05B037/02 |
Claims
1. An end-of-life detecting LED light bulb comprising: an LED light
bulb; and a microcontroller having a circuit for detecting
operational time of the bulb; and wherein the microcontroller turns
the bulb off upon reaching a preset amount of operational time.
2. An end-of-life LED light bulb as set forth in claim 1, wherein
the microcontroller counts AC line cycles.
3. An end-of-life LED light bulb as set forth in claim 1, wherein
the microcontroller includes a non-volatile memory.
4. An end-of-life LED light bulb as set forth in claim 3, wherein
the non-volatile memory is read from at bulb power-up and written
to at bulb power-down.
5. An end-of-life LED light bulb as set forth in claim 1, wherein
the circuit for turning off the bulb compares the output of the
circuit with a reference value.
6. An end-of-life LED light bulb as set forth in claim 2, wherein
the circuit for turning off the bulb compares the output of the
counter with a reference value.
7. An end-of-life LED light bulb as set forth in claim 5, wherein
the reference value is randomly adjusted at production time.
8. An end-of-life LED light bulb as set forth in claim 6, wherein
the reference value is randomly adjusted at production time.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to LED light bulbs which turn
themselves permanently off when they reach the end of their useful
life, and more particularly, to a scheme which slightly varies the
end-of-life condition from unit to unit, or light bulb to light
bulb.
BACKGROUND OF THE INVENTION
[0002] There are three major technologies used for light bulbs
today: incandescent, fluorescent and LED. Both incandescent and
fluorescent bulbs have a well-defined end-of-life. This occurs when
the filament breaks, and they cease producing light. Traditionally,
for a plurality of light bulbs, "end-of-life" of both incandescent
and fluorescent bulbs refers to the time when 50% of a population
of them no longer emits light. In addition, because of the careful
design of these bulbs, their end-of-life also corresponds to a
specific level of light loss, which ensures that when the bulb
needs to be replaced, it is at approximately the lowest acceptable
level of light output.
[0003] However, because of the physical nature of the failure mode,
there is naturally some distribution of failure times around this
mean, which is convenient in application, as it means that not all
the bulbs in a given install cycle fail simultaneously which might
potentially cause under-lighting.
[0004] In the case of LED bulbs, failures are rare and occur after
a very long time. Instead, the industry has chosen to define
"end-of-life" for an LED bulb as the time at which it produces
noticeably less light than initially, presently defined as 70% of
initial lumens.
[0005] For many applications, the very long life time of LED bulbs
is an advantage. Typically, most of these applications do not
require replacing the bulb just because some degradation in light
has occurred. However, there are other applications in which a
minimum light level is required. For example, work and/or office
areas can require a certain light level to ensure productivity,
and/or a certain light level to avoid eye strain among office
workers.
[0006] It can be appreciated that in circumstances such as these,
it would be desirable to have the ability to turn off the LED light
bulb when a specified level of light loss is reached. In addition,
in order to avoid having all or a majority of light bulbs in an
area turn off simultaneously, it would be desirable to have a
variation and/or distribution of turn off times (i.e., end-of-life)
of the light bulbs.
SUMMARY OF THE INVENTION
[0007] This invention has the object of developing an apparatus
with a controllable end-of-life such that the above-described
primary problem is effectively solved. In accordance with an
exemplary embodiment, it would be desirable to provide an LED light
bulb that after a predetermined amount of time turns itself off,
and wherein the predetermined time is variable or has some
variation thereto. In accordance with an exemplary embodiment, the
apparatus includes an LED light bulb, a circuit for counting AC
line cycles, a non-volatile memory for maintaining a record of the
bulb operational time while the bulb is off, and a circuit to shut
off the bulb when a preset amount of operational time has
passed.
[0008] In accordance with one embodiment, a microcontroller counts
AC line cycles using a resistor divider from the rectified AC line
and an edge-triggered digital input. Every time the line voltage
crosses some threshold, the resistor divider output triggers the
digital input of the microcontroller, causing it to increment an
internal counter by one. The counter may be preferentially arranged
to have enough bits to count line cycles during the entire
operational lifetime of the bulb.
[0009] During the time that the bulb is not energized, the counter
value may be offloaded to a non-volatile memory, preferentially
also inside the microcontroller. When the bulb is first turned on,
the value in the non-volatile memory may be downloaded to the
counter, so that the count continues from where it last left off In
accordance with an exemplary embodiment, the power circuitry inside
the bulb can be designed such that when power is cut to the bulb,
sufficient energy remains stored in an internal capacitor for the
microcontroller to offload the counter to the non-volatile memory
so that the count is not lost.
[0010] When the counter value reaches a predetermined value set in
the microcontroller's program, the bulb is turned off. If the bulb
is turned on when the predetermined value has already been reached,
the bulb fails to turn on, which ensures that once the bulb is
"dead" (i.e., the bulb has reached the end of its useful life or
"end-of-life"), it remains "dead".
[0011] Finally, the predetermined value may be set to varying
values in various bulbs in the factory. For example, a period of
one month could be set as the distribution of end-of-life times,
with 10% of the light bulbs coming off the line being in the first
tenth of that period, 10% of the light bulbs coming off the line
being in the second tenth of that period and so on. By staggering
or varying the time (or periods) in which light bulbs reach their
end-of-life, this ensures that no more than approximately one tenth
of the light bulbs will fail at any one time, reducing light output
by only one tenth, and ensuring that there is adequate time to
replace all of the light bulbs.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] The accompanying drawings are included to provide a further
understanding of the invention, and are incorporated in and
constitute a part of this specification. The drawings illustrate
embodiments of the invention and, together with the description,
serve to explain the principles of the invention. In the
drawings,
[0013] FIG. 1 is a cross-sectional view of a LED light bulb in
accordance with an embodiment.
[0014] FIG. 2 is a block diagram of a circuit used to count AC line
cycles to determine end-of-life of an LED bulb.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0015] Reference will now be made in detail to the present
preferred embodiments of the invention, examples of which are
illustrated in the accompanying drawings. Wherever possible, the
same reference numbers are used in the drawings and the description
to refer to the same or like parts.
[0016] According to the design characteristics, a detailed
description of the current practice and preferred embodiments is
given below.
[0017] FIG. 1 shows a cross-sectional view of an LED light bulb 10
showing the shell (or bulb) 20 enclosing an LED (light-emitting
diode) 30 according to one embodiment. The light bulb 10 includes a
screw-in base 40, which includes a series of screw threads 42 and a
base pin 44. The screw-in base 40 is configured to fit within and
make electrical contact with a standard electrical socket (not
shown). The electrical socket is preferably dimensioned to receive
an incandescent or other standard light bulb as known in the art.
However, it can be appreciated that the screw-in base 40 can be
modified to fit within any electrical socket, which is configured
to receive a light bulb, such as a bayonet style base. In use, the
screw-in base 40 makes electrical contact with the AC power in a
socket through its screw threads 42 and its base pin 44.
[0018] FIG. 2 is a block diagram of a microcontroller 100 and the
circuitry 110 of the microcontroller 100 used to count AC line
cycles to determine "end-of-life" of an LED bulb 10 as shown in
FIG. 1. In accordance with an exemplary embodiment, the circuit 110
includes an input (or input signal) 120 from a rectified AC line
122. The signal 120 is scaled by a resistor divider 130 comprised
of a first resistor 132 and a second resistor 134 to a level that
is useful as a microcontroller input in the form of a scaled AC
signal 136. Inside the microcontroller circuit 110 is a comparator
140, which receives the scaled AC signal or input 136 from the
resistor divider 130. The scaled AC signal 136 is compared by the
comparator 140 with a reference 142. In accordance with an
exemplary embodiment, the reference 142 is an internal voltage
reference 144. However, it can be appreciated that other references
142 can be used including but not limited to an internal current
reference. Preferentially, if the scaled AC signal (or input) 136
transitions from below the internal voltage reference 144 to above
it, the comparator 140 produces an output 152 in form of a pulse or
signal, which is fed to a counter 150. It can be appreciated that
in accordance with an alternative embodiment, the polarity could be
reversed, or alternatively, the comparator 140 output 152 can be
used to trigger an edge-detector (not shown).
[0019] The counter 150 counts line cycles (i.e., AC line cycles)
during the entire time the light bulb 10 is on (i.e., when a source
of power is being supplied to the bulb) producing a counter value.
When the bulb 10 is turned off or "power down" (i.e., the source of
power is removed or no longer provided to the bulb), the
microcontroller circuit 110 off-loads (i.e., writes) the counter
value to a non-volatile memory 160. The non-volatile memory 160
stores the sum of all the counter values (i.e., counts) to date
during the time the light bulb is off. When the light bulb 10 is
turned on or "power up", the counter value (or value) of the
non-volatile memory 160 is loaded (or read) into the counter 150,
so that the count may resume where the count was left off. In
accordance with an exemplary embodiment, when the light bulb 10 is
first turned on, the value of the non-volatile memory is preferably
set to zero (0).
[0020] In accordance with an exemplary embodiment, when the value
of the counter 150 reaches a pre-determined value, the
microcontroller circuit 110 writes the value to the non-volatile
memory 160 and shuts off the light bulb. If the input power to the
bulb is toggled, the microcontroller circuit 110 tests the value in
the non-volatile memory 160. If the value is at the pre-determined
limit, the microcontroller circuit 110 prevents the bulb from
turning on, and the bulb remains permanently "off", which ensures
that once the bulb is "dead" (i.e., the bulb has reached the end of
its useful life or "end-of-life"), it remains "dead". In accordance
with an embodiment, the pre-determined limit can be randomly
adjusted at production time to provide a plurality of lights bulbs
10 having variable end-of-life cycles or operational times. It can
be appreciated that by varying the end-of-life cycles for a
plurality of light bulbs, a scheme and/or method can be implemented
which slightly varies the end-of-life condition from unit to unit
(i.e., "light bulb to light bulb" and/or "location to
location").
[0021] In accordance with an exemplary embodiment, the circuit 110
can also include a power-on reset (POR) generator or other suitable
processor 170, which generates a reset signal when power is applied
to the circuit 110, which ensures that the microcontroller 100
starts operating in a known state.
[0022] It will be apparent to those skilled in the art that various
modifications and variation can be made to the structure of the
present invention without departing from the scope or spirit of the
invention. In view of the foregoing, it is intended that the
present invention cover modifications and variations of this
invention provided they fall within the scope of the following
claims and their equivalents.
* * * * *